Esters of pentavalent phosphorus acids and production thereof



United States Patent US. Cl. 260-963 9 Claims ABSTRACT OF THE DISCLOSURE Phosphoric esters of the formula wherein A and A are alkyl, alkoxy, aryl or aryloxy having a total of 2 to 22 carbon atoms therein, Y and Y are oxygen or sulfur, Z, Z, Z and Z are hydrogen, alkyl or chloroalkyl having a total of not more than 10 carbon atoms therein and X is chlorine or bromine produced by condensing a tautomer of the formula A Y A with a compound of the formula and halogenated hydrocarbon, which esters are useful as lubricant additives, plasticizers, insecticides, fungicides, etc.

This invention relates to a method of obtaining esters of pentavalent phosphorus acids and more particularly phosphoric esters of the general formula:

in which A and A represent individually radicals R, R or groups RO, RO, RS, R'S, or RRN, R and R, which may be identical or different, each representing a hydrogen atom, a saturated or unsaturated aliphatic or cyclic hydrocarbon radical, possibly substituted by halogen atoms, alcohol, ester or ether oxide functions, or nitrogen or phosphorus containing groups, R and R further possible being the monovalent extremities of a glycol or polyol of the type HORROH; Y and Y represent individually an oxygen or sulfur atom; Z, Z, Z", and 2, which may be identical or different, represent hydrogen or halogen atoms, or monovalent aliphatic or cyclic, saturated or unsaturated, halogenated or unhalogenated radicals; X is a halogen atom.

Certain known compounds derived from pentavalent phosphorus may be represented by a general formula similar to Formula I. Such known compounds are generally prepared in the following manner:

A halide such as dialkylphosphoryl chloride of Formula II hereafter is condensed:

Either with an alcohol of Formula III hereafter in or without the presence of a basic reagent capable of neutralizing the halohydric acid formed by condensation.

Or with an epoxide compound of Formula IV hereafter using a catalyst or not.

The respective formulae of the above mentioned compounds II, III and IV being:

in which R, R, Z, Z", Z' and X have the same meaning as above.

However, the known methods of preparation have substantial disadvantages. In the first place the use of an acid halide of Formula II hereabove as a reaction component gives rise to considerable practical difiiculties, since such halides have a corrosive action on the metals normally used for the manufacture of industrial apparatus.

Furthermore, compounds of Formula II have a tendency to disproportionation of the type according to the following reaction:

(1) R0 0 R0 0 R0 0 Consequently when a compound II condenses with products III or IV a single phosphoric ester I is not obtained, but a mixture of the desired ester I with byproducts resulting from the condensation of compounds III or IV with the products of the disproportionation of the acid halide II. In order to eliminate said by-products it is necessary to submit the reaction mixture to long and costly fractionating, and to isolate phosphoric ester I.

An object of our invention is to provide a method for the manufacture of phosphoric esters of the above mentioned type, by means of which the desired phosphoric ester or definite desired mixed esters may be obtained alone; without the necessity of isolating the said ester or esters from a reaction mixture.

Another object of the invention is to provide a method for the manufacture of such phosphoric esters which may easily be carried out on a commercial scale and in which corrosion hazards in the apparatus employed are reduced to a minimum.

These and other objects will be fully apparent from the following specification.

According to the invention at least one compound of Formula V hereafter, containing radical PY'H and having two tautomeric forms (Va) and (Vb):

is reacted with a compound of formula:

and a halogenated compound of formula XD, A, A, Y, Y, Z, Z Z, Z and X, having the same meaning as above, and D representing a monovalent, aliphatic or cyclic, saturated or unsaturated radical preferably containing one or more halogen atoms, the reaction being carried out at a temperature between 0 and 250 C., and preferably between 20 and C., in the presence or absence of a catalyst.

In the most simple instance the reaction according to the invention leads to the formation of the desired ester and of a hydride HD corresponding to halide XD used at the start.

The reaction can then be written as follows:

However, in practice, and particularly if radical D of compound XD used comprises halogen atoms, hydride HD may react in turn by one or several of the halogen atoms of D, thus giving a dihydride or a polyhydride. In this case it is also found that hydride HD spontaneously loses a molecule of halohydric acid, thus giving an olefin. In consequence, as a general rule the formation of a simple hydride HD is not necessarily a feature of the method of the invention.

As compounds V which may be used according to the invention preference is given to phosphorous acid, phosphonous or phosphinous acids (otherwise designated as secondary phosphine oxides), phosphorothioous acid, phosphonothioous or phosphinothioous acids (the latter otherwise designated as secondary phosphine sulfides) and monoesters, or diesters of said acids, or mixtures thereof in which the total number of carbon atoms in A+A' is 2 to 22. Typical compounds are monoor dimethyl phosphites, monoor diethyl phosphites, monoor dipropyl phosphites, diallyl phosphites, bis(2-chloro-ethyl) phosphite, diphenyl phosphite, cyclic or acyclic partial phosphorous esters of halogenated or unhalogenated glycols, triols or polyols, monoethyl N,N-dimethylphosphoramidite, 0,0-diethyl phosphorothioite, O,S-diethyl phosphorothioite, O,S-diethyl phosphorodithioite, S,S-diethyl phosphorodithioite, monobutyl methanephosphonite, monoethyl ethanephosphonite, monoethyl benzenephosphonite, 2-chloroethyl benzenephosphonite, monobutyl pchlorobenzene phosphonite, monophenyl p dimethylaminobenzenephosphonite, monoethyl p-anisylphosphonite, O-monoethyl methanephosphonothioite, S-monoethyl methanephosphonothioite, O-monoethyl benzenephosphonothioite, S-monoethyl benzenephosphonothioite; dimethylphosphinous, diethylphosphinous, diphenylphos phinous, di(p-chlorophenyl)phosphinous, di(p-tolyl)phosphinous, di (2,4-xylyl)phosphinous, bis (2,4,6-trimethyl phenyl)phosphinous, bis (2,3,5,6 tetramethylphenyl) phospinous and bis (2,3,4,5,6-pentamethylphenyl)phosphinous acid; dimethylphosphinothioous, dioctylphosphinothioous, and di(p-chlorophenyl)phosphinothioos acids; IO-hydroxy 5,10-dihydrophenophosphazine, and the like.

Compound V may also possibly be used in admixture with compounds containing no phosphorus or with phosphorus containing compounds which do not comprise radical PY'H and more particularly trivalent phosphorus esters such as, for example, phosphorus acid triesters or phosphorothioous acid triesters, phosphonous acid diesters or phosphonothioous acid diesters, phosphinous acid monoesters or phosphinothioous acid monoesters; in the latter cases, during the reaction, the said esters of trivalent phosphorus may either remain unchanged or be converted respectively into phosphonic or phosphonothioic diesters, phosphinic or phosphinothioic monoesters or into tertiary phosphine oxides r sulfides by thermal isomerisation or Michaelis-Arbuzov condensation with the haloalkyl esters of the type represented by hereinabove Formula I and originating from the phosphorus constituents comprising radical PYH.

The compound VI used is preferably taken from among ethylene oxide, propylene oxide, butylene oxide, styrene oxide, glycidyl esters or ethers, vinylcyclohexene monoor dioxides, dicyclopentadiene monoor dioxides, dipentene monoor dioxides, epihalohydrins, epoxidized oils and fatty esters, epoxy resins, ethylene episulfide, propylene episulfide, and the like. The total number of carbon atoms in Z-i-Z'+Z+Z"' is not more than 10.

Compound XD is preferably a polyhaloalkane containing 1 to 5 carbon atoms in which at least two of the halogen atoms are carried by the same carbon atom. Typical examples of such polyhaloalkanes are tetrachloromethane, trichlorobromomethane, dichlorodibromomethane, chlorotribromomethane, tetrabromomethane, chloroform, bromoform, iodoform, dichloromethane, dibromomethane, diiodomethane, hexachloroethane, hexabromoethane, pentachloroethane, pentabromoethane, pentabromomethane, 1,1,1,2-tetrachloroethane, 1,1,1,2-tetrabromoethane, 1,2- dibromo 1,l,2,2 tetrachloroethane, octachloropentanc, decachlorobutane, hexachloropropane, 1,1,2-trichloro-1- fluoroethane, 1,1,2,2-tetrachloro-l,2-difiuoroethane, 1,1,2- trichloro 1,2,2 trifluoroethane, ethyl trichloroacetate, chloral and acetals thereof, acetonechloroform and the like.

The respective quantities of constituents of the reaction according to the invention are not critical. Compound V containing radical PY'H and the epoxy compound VI are preferably used in stoichiometric proportion, whilst halide XD is used in excess.

The condensation according to the invention is generally carried out at atmospheric pressure, but pressures lower or higher than normal may be used, preferably pressures not exceeding 25 atmospheres.

It is not essential to use a catalyst, but in practice it is very advantageous to do so in order to increase the speed of reaction. Catalysts which may be used according to the invention are, e.g. anhydrous halohydric acids, halides of polyvalent metals such as aluminum, titanium, zirconium, antimony, lead, iron zinc, cadmium, nickel, cobalt, tin, hafnium, as well as organo-metallic compounds, possibly halogenated, derived from the same metals, such as tetrabutyl tin, dibutyl tin chloride, phenyl tin trichloride, tetrabutyl titanate, aluminum triethoxide and the like. The quantity of catalyst used does not usually exceed 2% of the total weight of reactives and should preferably be between 0.05 and 0.5% in relation to the weight of the reaction mixture.

If desired, condensation according to the invention may take place in an inert solvent which may be taken, for example, from among the non-reactive alkyl or arylhalides, ether-oxides, esters, and the like. An excess of halide XD may also be used as a solvent.

The invention allows esters of pentavalent phosphorus acids to be prepared easily and directly, and in particular definite mixed Z-haloalkyl phosphates. Such esters can find use as solvents, hydraulic fluids, plasticizers for synthetic plastics, additives for lubricants, fireproofing agents, anti-frothing agents, intermediary products, insecticides, fungicides and the like.

It is also possible to obtain according to the invention polyesters of pentavalent phosphorus acids and polyols which may contain particular atoms or radicals such as Cl, OH, etc., and which may be used as glues, additives for lubricants, basic polyhydroxylated materials for the manufacture of polyester or polyurethane resins, polymeric plasticizers, and the like.

The new process can also be used for the phosphorylation of substances comprising epoxy groups such as epoxidized oils, epoxy resins, monomeric or polymeric glycidic esters, and the like, in order to impart the same with particular properties such as improved resistance to flame, increased polarity, afiinity for certain dyes, lubricating qualities, adhesive qualities and the like.

Furthermore, the invention may be used to eliminate secondary phosphites or other organophosphorus compounds comprising radical PY'H from their mixtures with compounds containing no phosphorus or compounds which contain phosphorus but do not comprises radical PY'H. For example, When a tertiary phosphite (ROMP is condensed with a haloalkane RX, a certain quantity of secondary phosphites (RO) POH sometimes form alongside the phosphate R'PO(OR) resulting from the normal Michaelis-Arbuzov reaction, which results in the 5 final product having reducing properties and an undesirable sensitivity to hydrolysis.

In such cases simultaneous or subsequent treatment of ethyldichloropropyl phosphate presumably formula-ting as (C H O) P(O)OCH(CH Cl) TABLE III the reactional mixture by an epoxide IV and a halogenated compound XD according to the invention allows 5 Pment the secondary phosphites to be transformed into phos- 2 5 )2 )0 a 2) P 01 no 5. MR phoric esters which no longer have the same drawbacks. Found u u 92 2589 M481 M772 55.57 EXAMPLE 1 Calculated 11.69 26.79 56. 24 Diethyl fi-chloroethyl phosphate EXAMPLE 5 41.4 g. (0.3 mole) diethylphosphate (phosphonate) Diethyl-fi-bromoethyl phosphate CHO PHOWe lacd' atol 10 'th 5 g fi g i g gg i g i j 223 41.4 g. (0.3 mole) dlethylphosphite, dissolved in 100 mole) ethylene oxide. The mixture was cooled to ml. anhydrous peroxide free ethyl ether and cooled to 0 and 3 drops of titanium tetrachloride were added. The Wer e added with mole) ethylene oxlde autoclave was then closed, kept in cold during 3 hours then with 59.5 g. (0.3 mole) trrchlorobromomethane and and then heated for another 3 hours at C Where finally with 5 drops titanium tetrachloride. The mixture after it was cooled and opened. The contents of the autowas allowefi f react at room temperature for 45 hours clave was distilled first at atmospheric pressure and then and then dlstlllfid under reduced pressure- A fracunder a vacuum. 20 tion was collected at :124125 C. (1 mm. Hg), the

A fraction weighing 49.2 g. (yield=76%) was colanalysis of which agreed with the formula lected at 103106 C. (0.5 mm. Hg.) Table I hereafter shows that said fraction was diethyl fl-chloroethyl phos- (C2H5O)2PO(OCH2CH2Br) phate (C H O) PO(OCH CH C1). as shown in Table IV hereafter.

TABLE IV Br, percent (CzH5O)2PO(OCzH4Br) P, percent Volumetric Gravimetrie 1113 d4 MR Found 12.22 30. 04 29.0 1. 4430 1.3750 50. Calculated 11.87 30.65 30.65 49. 6

TABLE I Percent Molar refrac- Combined Combined (CZH5O)ZPO(OCZH4CI) P Cl m; (14 tion (MR) H3130; per- HsPOi per cent cent Found 14.05 15.43 1.4270 1.1874 46.79 0.54 41.8 Calculated 14.35 16.4 46.765 0 45.3

EXAMPLE 2 The agreement between the result of both the volu- Example 1 was repeated Without use of titanium tetra metric and gravimetric bromine argentometric titration chloride. Diethyl-fi-chloroethyl phosphate was again ob- 2 i the .halogen contained m the condensate 1S tained but with a yield of 5% only. 6 Y mmme- EXAMPLE 3 EXAMPLE 6 Diethyl chloropropyl phosphate D iphenyl'fi'chlomethyl phosphate 4 62 g. (0.2 mole) triphenylphosphite were heated un- 41.4 g. (0.3 mole) diethyl hos hite were treated as in Example 1, with 93 g. (0.6 r nole tetrachloromethane, der.ag1tatl0n Wlth 1, mole) phosphorous q 20.9 g. (0.36 mole) propylene oxide and 3 drops of tidurmg 1 at to produce.o'3 mole crud? d1- tanium tetrachloride with the only difference that the Phenylphosphlte; 3 dlphenylphosphlte was placed an hot treatment step was carried out at C. during 3 autoclave along w1th 19.8 g. (0.45 mole) ethylene oxide, hours. Distillating of the raw product under vacuum 93 mole). tetrachloromethane 3 drops yielded a fraction of 205 g collected at 924000 c (0 4 conium tetrachloride. The autoclave was closed and heated Hg), which as show'n in Table H hereafter' at 100 for 3 hours. It was then cooled, opened and the diethyl chloro propyl phosphate presumably formulating crude product was distllled under reduced pressure. 12.7 as (C H O PO(OCH CHClCH g. pure (C H O) PO(OCH CH Cl) were obtained,

B.P.=175-178 C. (0.5-1 mm. Hg):

TABLE v TABLE II Percent Percent (CBH50)2PO(OC2H4CD P Cl nn di MR (C2H50)2PO(OC3H6C1) P 01 [1 5 MR Found 10.11 11. 39 1. 5240 1.2655 75.7 Calculated 9. 02 11.37 76.50 55 5-5 5-22 5 .152

e EXAMPLE 7 Chloro-pentaerythritol, polypropyleneglycol and chloroethyl mixed phosphate-phosphonate (phosphorus and EXAMPL 4 chlorine containing polyol) Diethyl-dichloropropyl phosphate A raw mixture of secondary and tertiary phosphites The reaction of Example 3 was repeated using 33.3 g. (1395:1637, (31% :71?) first Prepared reacting (0.36 mole) glycerol epichlorhydrin instead of propylene- 3 y Pentaerythntol Wlth 1237 3 Phosphorus oxide. Disstillation under vacuum yielded at 118-420 C. chlorlde- (1.35 mm. Hg.) a fraction weighing 23.9 g. which, as 50 g. of sa1d mixed phosphites were placed in a presshown by Table III hereafter was identified as pure di- 75 sure reactor along with 50 g. polypropyleneglycol (mean 7 MW=200), .18 g. ethylene oxide, 307 g. tetrachloromethane and drops titanium tetrachloride. The reactor was closed and then heated and shaked at 120 C. for hours during which time the dialkyl (secondary) phosphites were converted to dialkyl chloroethylphosphates and 4.77%) agreed with the hypothesis of an incomplete reaction according to:

and the trialkyl (tertiary) phosphites were converted to 5 phosphonic acid esters, according to the well known N /N\ Michaelis-Arbuzov reaction. Eventually the volatile Inat- 01 ters were distilled under vacuum at 100 C. The residue m was a gold yellow viscous oil, P%=8.74; Cl%=5.13; 10 \P I I acid value=0.l0 (mg. KOH/g.); hydroxyl value=320; y 0 phosphorous acid esters (expressed as elemental phos- 0 H 0 00111011191 phorus)=1.63.

EXAMPLE 8 Ethyl S-chloroethyl benzenephosphonate EXAMPLE 11 12 g. (0.07 mole) ethyl hydrogen benzenephosphonite fl-chloroethyl bis(2,4,6-trimethyl phenyl) C H P(O)H(0C H were placed in an autoclave along phosphinate: C H ClO P with 6.6 g. (0.15 mole) ethylene oxide, 54.5 g. (0.35 mole) tetrachloromethane and 3 drops titanium tetra- 20 BIS (246'mmethy1phenynphosphmous acid chloride. The mixture was allowed to react at atmospheric [(CH C H i fgg y: 3 and then heated for 31/2 hours PHO was prepared by condensation of mesitylene with B g g gf e the crud r d ct 12 phosphorus trichloride, according to A. W. Frank, Joury y 5 mg e p o u nal of Organic Chemistry, 1959, 24, 966. Said compound (y1eld=69%) C H PO(OC H (OCH CH CI) were Obtained B P 130 135 C 5 0 6 mm H was obtained as a vitreous, substantially colorless mass g having the following characteristics (unpublished up to TABLE VI the present time) Yemen B.P.=220230 C. (0.60-0.65 mm. Hg) cart-Po(oogmxociulol) P 01 mm an MR n =l.590O, d =1.0788 2 51113113 12.28 13.91 1.5091 1.220 68.0? P%:10-30 (th6OrY=10-83) Qua e 6 Reducing phosphorus (oxidation by alcoholic iodine) =9.85% Cl% =0.83. EXAMPLE 9 25.5 g. (0.089 mole) of said compound were placed Diethyl fl-chloroethyl phosphorothlonate 35 in an autoclave along with 12.8 g. (0.29 mole) ethylene A mixture of 30 (0.195 mole) OOdiethfi phos oxide, 80 g. (0.52 mole) tetrachloromethane and 5 drops phorothioite (C2H5O)2PHS 172 (0.39 mole) ethylene titanium tetrachloride and the mixture was heated under oxide, 140 g. (0.91 mole) tetrachloromethane and 2 drops Pressure at durmg 4 hours After 9001' titanium tetrachloride was allowed to react overnight at 40 mg the cPntents of the autoclave Was eyaporated 10 C011- atmospheric temperature and then heated in an autoclave Stant Welght The residue (Whlch no longer at 100 C. during 3 hours mn. After cooling, the a duced alcoholic iodine) was dissolved in a 1/1 mixture clave was Opened; the nasty odour of diethylphosphoro of benzene and hexane; the solut on, separated from an thioite had disappeared. The crude product was twice msoluble mlknown 9 by filtfatlon, Was evaporated to fractionally distilled under reduced pressure, yielding a 45 constant Welght t0 yleld a liquid ViSCOHS sidue of crude 9 g. fraction, the characteristics of which agreed fairly 3)3 5 z]2' O(OC CH C1)I P%-=8.37; Cl%: with the formula (C H O) PS(OC H CI) and with the 6; acid value=0 (calculated for C H CIO P: P%'= literature: 8.51, Cl% =9.74.

TABLE VII Percent (CzHsO)zPS(OCzH4Cl) P C] B.P./mm. Hg n0 d4 MR Found 12.5 16.2 61. 9/0. 45 1.4660 1.1797 54.65 Calculated or lit 13.33 15.27 107-121/4-5 1.4652 54.23

1 V. G. Pesin and A. M. Khaletskii, Zhurnal Obshechej Khirnii 1961, 31, 2508 The obtained compound was further characterized and the thionate structure thereof confirmed by preparation of a double salt, through heating it with two equivalents of HgI at 130-135 C., whereby z 5 )z z 4 z] was obtained in the form of yellow needles which, after three recrystallizations from methanol, melted at 97- 98 C.

EXAMPLE 10 10-oxo, 10-chloroethoxy, 5, 10-dihydrophenophosphazine EXAMPLE 12 The process of Example 8 was repeated, using 150 g. diethyl phosphite, 500 g. epoxidized soybean oil containing 5.71% oxiranic oxygen, 250 g. tetrachloromethane and 4 gr. tin tetrachloride. The mixture was left at rest for 24 hours at room temperature, then heated for 8 hours at C., then for 2 hours at C. and finally for 1 hour at C. After cooling, the autoclave was opened and the volatile components were evaporated under vacuum. 685 gr. of an oily residue were obtained, -P% =4.91; Cl% =5.33. Said product is effective as an unctuousness additive for lubricant.

Although our present invention has been more particularly disclosed in the above examples of preferred embodiments it will be apparent to anyone skilled in the art that various modifications may be made thereto without departing from the spirit and scope thereof.

9 What We claim is: 1. A method for the manufacture of esters of pentavalent phosphorus acids of the formula A\fi'l Z %I/ /PYC('3X A! Z! Z!!! wherein A and A are selected from the group consisting of alkyl, alkoxy, monocyclic aryl and monocyclic aryloxy, the total number of carbon atoms in A+A being 2 to 22, Y and Y are selected from the group consisting of oxygen and sulfur, Z, Z, Z and Z being selected from the group consisting of hydrogen, alkyl and chloroalkyl, the total number of carbon atoms in Z+Z'+Z {Z"' being not more than 10 and X is a halogen selected from the group consisting of chlorine and bromine which comprises the steps of condensing at a temperature of to 250 C. a compound containing the radical PY'H selected from the tautomeric forms of the group consisting of \PY-1[ A A wherein A, A and Y' have the above definitions with a compound of the formula wherein Y, Z, Z, Z and Z have the above definitions and with a halogenated compound of the formula wherein X is selected from the group consisting of chlorine and bromine and D is an alkyl of l to 5 carbon atoms having at least one halogen selected from the group consisting of chlorine and bromine, whereby an impure reaction product is obtained and distilling said esters of pentavalent phosphorus acids from said impure reaction product.

2. The method as claimed in claim 1, wherein said compound containing radical PYH is a phosphorus acid ester.

3. The method as claimed in claim 1, wherein said compound containing radical PYH is a phosphonous acid monoester.

4. The method as claimed in claim 1, wherein said compound containing radical PYH is a phosphinous acid.

5. The method as claimed in claim 1, wherein said compound containing radical PYH is a phosphorothioous acid ester.

6. The method as claimed in claim '1, wherein said halogenated compound XD is a polyhaloalkane containing 1 to 4 carbon atoms and in which at least two halogen atoms are carried by the same carbon atom.

7. The method as claimed in claim 1, wherein said compound having the formula is a member selected from the group consisting of ethylene oxide, propylene oxide, butylene oxide, styrene oxide, glycidyl esters, glycidyl ethers, vinylcyclohexenemonooxides, vinylcyclohexenedioxides, dicyclopentadienemonooxides, dicyclopentadienedioxides, dipentenemonooxides, dipentenedioxides, epihalohydrins, epoxidised fatty esters, ethylene episulfide and propylene episulfide.

8. A method for the manufacture of mixed phosphoricphosphonic esters of chlorinated pentaerythrite, polypropylene glycol and chloroethyl which comprises the steps of reacting one mole of phosphorus trichloride with about 0.75 to 2 moles of pentaerythritol, whereby a mixture of secondary and tertiary chlorinated pentaerythrite phosphites is obtained, dissolving said mixture in a substantially equal weight of a polypropyleneglycol of a molecular Weight comprised between 134 and 308, adding tetrachloromethane and ethylene oxide thereto and heating the resulting mixture at substantially C. in the presence of titanium tetrachloride as catalyst, whereby a reaction product containing volatile substances is obtained, and distilling said reaction product to expel said volatile substances.

9. A mixed, chlorinated pentaerythrite, polypropylene glycol and chloroethyl phosphate-phosphonate prepared according to the method of claim 8.

References Cited UNITED STATES PATENTS 3,100,220 8/1963 Smith 260-963 3,206,495 9/1965 McBee 'et a1. 260963 FOREIGN PATENTS 1,133,060 1960 U.S.S.R.

OTHER REFERENCES Cram et al., Organic Chemistry, Second Edition, Mc- GraW-Hill, New York, p. 250, 1964.

CHARLES B. PARKER, Primary Examiner. ANTON H. SUTTO, Assistant Examiner.

U.S. Cl. X.R. 

